* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download View File - University of Engineering and Technology, Taxila
Survey
Document related concepts
Deep packet inspection wikipedia , lookup
Asynchronous Transfer Mode wikipedia , lookup
Wake-on-LAN wikipedia , lookup
Distributed firewall wikipedia , lookup
Zero-configuration networking wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Piggybacking (Internet access) wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
Computer network wikipedia , lookup
Network tap wikipedia , lookup
Transcript
Lecture # 01 Introduction Course Instructor: Engr. Sana Ziafat Grading Policy Final Exam: Mid term Exam Assignments Quizzes: Lab work 40% 20% 5% 15% 20% Quizzes may be announced or unannounced. Exams are closed-book and extremely time limited. Exams consist of design questions, numerical, maybe true-false and short answer questions. TEXT BOOKS Data Communications and Networking, 4/e B.A. Forouzan, McGraw-Hill, 2003, ISBN 0-07-292354-7. Data and Computer Communication by William Stallings (7th Edition) Prentice Hall. Introduction Data : Refers to information presented in whatever form is agreed upon by the parties creating and using data Communication: When we communicate we are sharing information. This sharing can be remote or local…. Local face to face and remote at a distance What is data communication? Data communication Exchange of data between two devices via some form of transmission medium such as wire cable. Defined as a subset of telecommunication involving the transmission of data to and from computers and components of computer systems. History of Telecommunications Invention of telegraph Samuel Morse – 1837 Invention of telephone- Alexander Graham Bell – 1876 Development of wireless By ??? – 1896 Concept of universal access and growth of AT&T Divestiture of AT&T—what year?? History of Telecommunications Continued…. Telecommunications Act of 1996 Three main developments that led to the growth of data communications systems: Large-scale integration of circuits reduced the cost and size of terminals and comm equipment Developments of software systems made establishment of communication networks easy Competition among providers of transmission facilities reduced the cost of data circuits Fundamental Characteristics The effectiveness of a data communication system depend on four fundamental characteristics: Delivery Accuracy Timelines Jitter (variation in packet arrival time) A Communications Model Source Generates data to be transmitted Transmitter Converts data into transmittable signals Transmission system Carries data Receiver Converts received signal into data Destination Takes incoming data Simplified Communications Model Diagram Simplified Data Communications Model Key Communications Tasks Transmission system utilization Interfacing Signal generation Synchronization Exchange management Error detection and correction Addressing and routing Recovery Message formatting Security Network management Data REPRESENTATION Data can be represented as 1. Text 2. Numbers 3. Images 4. Audio 5. Video Direction of data flow Simplex Half Duplex Full Duplex Before looking inside a computer network, first agree on what a computer network is Computer network ? Specialized to handle: Set of serial lines to attach terminals to mainframe ? Telephone network carrying voice traffic ? Cable network to disseminate video signals ? Keystrokes Voice Video Networks Potential of networking: move bits everywhere, cheaply, and with desired performance characteristics Network provides “connectivity” What is “Connectivity” ? Direct or indirect access to every other node in the network Connectivity is the magic needed to communicate if you do not have a direct pt-pt physical link. Tradeoff: Performance characteristics worse than true physical link! A Network A network can be defined recursively as two or more nodes connected by a physical link Or two or more networks connected by one or more nodes Network Hardware Transmission Technology Broadcast/ Multipoint Network Point – To – Point Network Single communication channel that is shared by all the machines on the network. Many connections between individual pairs of machines All the others receive “Packets” in certain contexts, sent by any machine. A packet may have to visit one or more intermediate machine. An address field within the packet specifies for whom it is intended. Routing algorithms play an important role in PTP networks. Multicasting: transmission to a subnet of the machines. Types of connections: point-to-point and multipoint Simplified Network Model Building Blocks Nodes: PC, special-purpose hardware… hosts switches Links: coax cable, optical fiber… point-to-point multiple access … Switched Networks A network can be defined recursively as... two or more nodes connected by a link white nodes (switches) implement the network colored nodes (hosts) use the network Switched Networks A network can be defined recursively as... two or more networks connected by one or more nodes: internetworks white nodes (router or gateway) interconnects the networks a cloud denotes “any type of independent network” Switching Strategies Circuit switching: carry bit streams a. b. c. d. establishes a dedicated circuit links reserved for use by communication channel send/receive bit stream at constant rate example: original telephone network • Packet switching: store-and-forward messages a. operates on discrete blocks of data b. utilizes resources according to traffic demand c. send/receive messages at variable rate d. example: Internet Networks: key issues Network criteria Performance Transit time Throughput Delay Reliability Data transmitted are identical to data received. Measured by the frequency of failure The time it takes a link to recover from a failure Security Protecting data from unauthorized access Terminology The throughput or bandwidth of a channel is the number of bits it can transfer per second The latency or delay of a channel is the time that elapses between sending information and the earliest possible reception of it Network topologies Topology defines the way hosts are connected to the network Network topology issues A goal of any topology 1. high throughput (bandwidth) 2. low latency Categories of Topology devices) Advantages & disadvantages of mesh topology Advantages - Dedicated links eliminate the traffic problem -Secure communication -Ease of fault identification & fault Isolation -Robust Disadvantages -Large number I/O ports & cabling required -Installation & reconfiguration is difficult -Wiring can be greater than available space -Expensive A star topology connecting four stations Advantages & disadvantages of star topology Advantages -Less expensive than mesh topology -Installation & reconfiguration are easy -Robust - Ease of fault identification & fault Isolation -Required less cabling than mesh topology Disadvantages -Dependency of whole topology on single point Application: High Speed LAN A bus topology connecting three stations Advantages & disadvantages of bus topology Advantages -Ease of installation -Required less cabling Disadvantages -Difficult reconnection &fault isolation -A fault or break stops all transmission A ring topology connecting six stations Advantages & disadvantages of bus topology Advantages -Ease of installation & reconfiguration Disadvantages -A break in ring can disable the entire link A hybrid topology: a star backbone with three bus networks What next ? Hosts are directly or indirectly connected to each other Nodes must be able to say which host it wants to communicate with Addressing and Routing Address: byte-string that identifies a node usually unique Routing: forwarding decisions process of determining how to forward messages to the destination node based on its address Types of addresses unicast: node-specific broadcast: all nodes on the network multicast: some subset of nodes on the network Wrap-up A network can be constructed from nesting of networks An address is required for each node that is reachable on the network Address is used to route messages toward appropriate destination LAN, WAN & MAN Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network) Network in a City is call MAN (Metropolitan Area Network) Network spread geographically (Country or across Globe) is called WAN (Wide Area Network) Local Area Networks Smaller scope Building or small campus Usually owned by same organization as attached devices Data rates much higher Usually broadcast systems Now some switched systems and ATM are being introduced Local Area Networks (Cont.) NETWORKS LAN MAN WAN INTERNET LAN CHARACTERISTICS Size Restricted in Size Transmission Technology Single Cable 10 to 100 Mbps Low delay (ms) Very few Errors Megabits/Sec. (Unit) Topology BUS (Ethernet) Ring (Token ring) MAN Metropolitan Area Network Support data and voice No switching elements Two unidirectional buses to which all the computers are connected. Each bus has a head-end, a device that initiates transmission activity. Traffic that is destined for a computer to the right of the sender uses the upper bus, traffics to the left uses the lower one. Wide Area Networks Large geographical area Alternative technologies Circuit switching Packet switching Frame relay Asynchronous transfer mode (ATM) Internet Collection of interconnected networks. Example: A collection of LAN’s connected by a WAN. Applications E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio Research areas in Networking Routing Security Ad-hoc networks Wireless networks Protocols Quality of Service … COURSE OUTLINE Network Models Encoding Schemes Bandwidth Utilization Different types of transmission medium Error detection & Correction IP addressing … Readings Chapter 1: 1.1, 1.2 Data & Computer Communication seventh Edition , By William Stallings Chapter 1: 1.1, 1.2 (B. A Forouzan) Data Communications and Networking, By Behroz A Forozun Q&A